As sampling frequency / sample rate is the number of cycles per second in sound, this may not be applicable to RealSense cameras. I wonder if you want to set the 'frame rate' of the camera, which is measured in Frames Per Second (FPS)?
If this is the case, then you can select a particular FPS rate (30 or 60) by setting a particular resolution for the color, depth or IR cameras. The values below for the SR300 are taken from its data sheet document.
In the '2016 R2' and '2016 R3' versions of the RealSense SDK in Windows, you can use the STREAM_TYPE_COLOR AND STREAM_TYPE_DEPTH instructions to set the resolution (and therefore the frame rate). for example, you could set a color resolution of 640x480 and an FPS of 60 with:
sm.EnableStream(PXCMCapture.StreamType.STREAM_TYPE_COLOR, 640, 480, 60);
The first two numbers set the resolution (640, 480 is 640x480 resolution). The third number on the end (60) is the FPS. So by setting it at 60, you have set it as 640x480 resolution at 60 FPS.
If you wanted to set the stream type to color instead of depth, it would be:
Please let me know if it was not the Frames Per Second that you were trying to set, and I will investigate your question further.
If you wanted to analyze data as slow as 1 FPS using the Windows '2016 R2' or '2016 R3' SDKs then you would need to pause the stream, check a frame and then un-pause and tell the camera to move on to analyzing the next frame.
The best tutorial for learning how to do this is linked to below, which takes you through the pause-analyze-unpause process step by step with sample scripting.